My Lennox Elite periodically shuts off or won't start back up. I have replaced the thermostat. I have it set at 68-70. some mornings I wake up and it is 60 or below and no furnace. If I turn the thermostat down and then back to 68-70 it will turn back on. That is why I started with replacing the thermostat but that wasn't it. Any help would be greatly appreciated.
You may want to take a picture on the furnace and also a picture of the control board inside. this may give us a better idea of what you have. Also post the model of the furnce but if you don't know then pics should be good.